Metal complexes, such as those containing radioactive metals, are useful as diagnostic and therapeutic agents. Complexes containing bioactive moieties capable of being selectively taken up at a desired site to facilitate evaluation or treatment of a subject are of particular interest. For example, U.S. Pat. No. 5,608,110 discloses compounds containing a heteroatom-bearing bridge which may be complexed with a metal and used in diagnostic and therapeutic methods. Although U.S. Pat. No. 5,741,912 discloses methods for preparing a variety of such compounds, there remains a need for simplified methods of synthesizing these compounds. The present invention addresses the need in the art for improved and simplified methods of synthesizing ligands for use in metal complexes, particularly complexes containing hypoxia-localizing moieties.